I. FIELD OF THE INVENTION
This invention relates to a printing mechanism of a recorder used for an enlarging copy machine or the like for enlarging and printing the image data read from documents.
II. DESCRIPTION OF THE PRIOR ART
Conventionally, a printing mechanism of a recorder for printing through a repeated movement of a printing head in a main scanning direction, includes a thermally sensitive recording head which has been disclosed in Japanese Utility Model Registration Patent Publication No. 4-50123 in 1992.
The thermally sensitive recording head disclosed by such publication comprises a base moving along a guide shaft, an attachment rotatably attached of its one end on the base, and a heating head rotatably provided on a tip end of the attachment, whereby the printing is achieved in that the heating head is pressed on thermally sensitive recording papers and the base repeatedly moves on the guide shaft arranged in the main scanning direction.
Heretofore known is the enlarging copy machine which reads the documents such as A4 size or the like by an image sensor, data-processes thus read image data, and prints the resultant data in enlarged sizes such as A1 or A0 or other sizes. In the enlarging copy machine of this kind, a plurality of printing heads are aligned at predetermined interval in the scanning direction, and each printing head is made to print over a length which is produced in that an entire line-length in the recording paper is partitioned by the number of printing heads.
When the conventional printing mechanism as formerly described is applied to the enlarging copy machine as immediately previously described, the plurality of printing heads are required to be arranged at a predetermined interval on the base that moves along the guide shaft. In concrete, a plurality of attachments, which supports on its tip ends the printing heads, are required to be mounted on each base whose dimension is lengthened corresponding to the number and the position of printing heads.
However, such arrangement makes the base overly lengthy, and a plurality of bearings for supporting the guide shaft must be provided on the base. For this reason, when a slight center-displacement of the bearing is present if any, then non-ununiformity of quality in the mechanism arises together with disturbance of a smooth sliding movement of the base along the guide shaft. When a certain clearance is provided between the bearing and the guide shaft, a mechanical accuracy deteriorates with backlash arising, and in addition, unwanted vibration on moving is generated even in slight clearance. Particularly, the vibration travels to the printing head to considerably deteriorate a printing image quality in the case where a high printing image quality is required as in the enlarging copy machine having a half tone (intermediate tone) printing mode.